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 Water Quality Advisory Lifted for Surviving Homes & Completed Construction: Updated May 20, 2020

How is your water treated?

Untreated water is conveyed directly from Paradise Lake or Magalia Reservoir to the water treatment plant (located just below Magalia dam) via either the Magalia Reservoir Bypass Pipeline, which is water from Paradise Lake, or the intake structure at Magalia Reservoir.  Typically, the majority of the water treated at the plant comes from the Bypass Pipeline; Magalia Reservoir is used for short periods of time, typically in the fall and winter, but could be any time. 

Water treatment transforms raw water into safe drinking water through the removal of solids (mainly mineral and organic particles) and disinfection. Our multi-step treatment process assures that California health requirements are met and safe, potable water is delivered to PID customers at all times.

Treatment Plant Operator

Disinfection—Chlorine is added (1.5 to 1.7 ppm) to kill or inactivate disease-causing organisms which may be present in the water (disinfection), control the growth of algae and assist with coagulation.

Coagulation—Coagulation consists of adding aluminum sulfate, aluminum chlorhydrate and two polymers to the raw water to chemically bond very small particles (turbidity) into larger particles (floc). Most of these larger floc particles are removed from the raw water as they pass through a bed of coarse, granulated media in the up-flow clarifiers.

Filtration—The clarified water then flows downward through tri-media filters (consisting of an-thracite, sand and fine garnet) to remove additional (turbidity and floc) particles which may still be in the water.

Tank time—After the two filtration processes the water is well below the State requirements for turbidity (0.2 NTU). The water is routed through a treated water storage tank which provides sufficient chlorine contact time to thoroughly disinfect the water. A minimum amount of chlorine remains (1.0 ppm) in the treated water to ensure the California health requirements are met in the distribution system so the potable water is delivered properly to the consumer at all times.

Corrosion protection—Finally, as the treated water leaves the plant, zinc orthophosphate (a corro-sion inhibitor) is added. This is added to minimize corrosion of the District’s steel pipelines, and minimize lead and copper leaching from customers’ pipes and faucets.



Fluoride is not added to our treated water, nor is it detectable in the raw water.


Wastewater is generated during the daily cleaning of the up-flow clarifiers and gravity filters. About eight to ten percent of the daily raw water is used to clean the clarifiers and filters (about 600 acre-feet per year). The wastewater is stored temporarily in a holding tank at the plant, dechlorinated and a polymer is added. This water is transferred to the settling ponds for liquid/solids separation. Clarified water is discharged to the Magalia Reservoir, and is regulated with a National Pollutant Discharge Elimination System (NPDES) permit. The settled solids in the ponds are dried when the ponds are taken out of service and drained. Dried solids are analyzed per landfill requirements and transported by the District to the local Neil Road Landfill.

The treatment plant was constructed in 1994 and went online in 1995. The plant has the flexibility to operate with computer or manual control. The automated operating system includes over 40 different alarms to monitor and advise the plant operators of unusual conditions. Operating information is archived both as part of the computer control system and recording charts. The plant includes an emergency generator that will operate the plant during a power outage. The treatment plant has plenty of capacity (flow tested at 22.8 million gallons/day) to meet current maximum daily and future demand. At times water is treated and delivered to the Del Oro Water Company, using water that they added to Paradise Lake.

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